There is slim to no chance at all with a male and just forget it with the female, its as rare as a swimming pool in a desert...and i don't mean at a resort. You could find a cockatiel talk one in a hundred thousand but well.....to each their own...if you want to try your luck.
And yes, birds can get injured from banging into something and not show it then just die due to internal bleeding and injuries to organs tearing. And too much protein....bad water...and .birds can also be carriers of something and never show sick but pass things on..these could all be the culprit for the death of a bird. Since it's just too months old, the budgie hadn't been eating long enough of the pellets so it must be something else like the egg powder mix and the above that I just mentioned.
well....if you really meant it slided down on the floor, it shouldn't have hurt much, and if he didn't get hurt at all, then mostly he died because of his diet/water or anything in the house that you didn't notice that is posing danger to the bird.